1. Field of the Invention
The present invention relates, in general, to torch tips and to a method of making torch tip pieces.
2. Description of the Prior Art
Torch tips, which are also known as blowpipe tips or cutting tips, serve to direct a stream of oxygen for cutting metals. The oxygen so directed passes through a central orifice in the tip called the cutting orifice. Surrounding the cutting orifice are a plurality of smaller orifices called the preheat orifices. A mixture of fuel gas and oxygen is passed through the preheat orifices to preheat the metal for cutting and to insulate the cutting oxygen from contamination by the surrounding air. To properly perform this function, the preheat orifices must be located precisely around the cutting orifice in a proper orientation. Torch tips with these features have, in the past, been made by three basic methods producing two basic styles of tips.
The older style is the single piece torch tip. One way of making this style of tip is by drilling. First, a solid blank of material, such as copper, is shaped in the form of a torch tip. Next, the cutting orifice and the preheat orifices are formed in the blank by drilling. Since drilled holes are limited in the minimum diameter attainable, it is often desired to make the orifices smaller. This improves their combustion properties such that the fuel gases more efficiently heat the workpiece. In this first method, this has been done by inserting piano wires in the drilled holes, swaging the tip around the wires, and then pulling the wires free. The problem with this method is that it is slow, the drills do not drill straight enough to optimally locate the orifices, the drills break frequently, and it is limited in the number of preheat orifices which can be located about the cutting orifice.
Another method of making the single piece type of tip is by swaging or drawing together two separate pieces. U.S. Pat. Nos. 3,716,902 and 2,254,757 reveal such a method. First, an outer piece is formed with longitudinal slots along its interior. Next, an inner piece, with a drilled cutting orifice, is placed inside the outer piece. Piano wires of the proper size are positioned in the appropriate locations. Finally, the composite of the inner and outer pieces is swaged together to the proper size and the wires are removed. This method is less expensive than the first method but problems remain. In this method, the number and shape of the preheat orifices is still limited, since the columns between the orifices must support the outer piece against the swaging force. Moreover, the ability to precisely orient the preheat orifices is less than optimum.
The other style of torch tip is a two piece design. An example of this type of tip is revealed in U.S. Pat. No. 2,468,824. The outer piece of this type of tip is made by forming a shell with a smooth interior. The inner piece is made by milling rectangular slots into the exterior of a blank piece of metal and drilling a cutting orifice into the center thereof. The smooth inner surface of the outer piece and the milled slots of the inner piece combine to form preheat orifices. By using a milling process, an increased number of preheat orifices is possible. Since gases other than acetylene require more preheat orifices due to their lower burning temperature, this type of tip is the type most desired for these other gases. Another advantage of this type of tip is its interchangeability. Due to rough handling, torch tips often are damaged while in use. The two piece design allows the inner or outer piece to be replaced without replacing the entire tip. Its disadvantage is that when a large number of slots are milled into the outer surface of the inner piece, thin "vanes" are formed which are easily broken. This subjects the inner piece to being easily damaged, especially during the process of interchanging pieces. In addition, the milling process often leaves burrs or other irregularities in the slots which cause improper burning through the preheat orifices. Finally, milling slots into the inner piece is limited in the shapes of preheat orifices which can be created. Thus, only rectangular slots, with vertical walls or slots which increase in size radially outward are possible.